If you have the ends off you may as well do them all at once, it is actually easier to do if the flyscreen is intact, it is better to get the job done as soon as the flyscreen start deteriorating as the rest will follow soon after.
If the screen is still relatively intact you have a shape to work with and can just sew the replacement on the inside and then cut the old flywire out afterwards, when the old screen is cactus it is a pain to get the right shape.
If the screen is still relatively intact you have a shape to work with and can just sew the replacement on the inside and then cut the old flywire out afterwards, when the old screen is cactus it is a pain to get the right shape.